2D Physics Simulator

#include <iostream>
#define _WIN32_WINNT 0x0500      //needed by gotoXY function only.
#include "Windows.h"             //needed by gotoXY function only.
using namespace std;

//gotoXY function, puts the cursor to x,y coordinate
void gotoXY(int x, int y)
{
  static HANDLE h = NULL;
  if(!h)
    h = GetStdHandle(STD_OUTPUT_HANDLE);
  COORD c = { x, y };
  SetConsoleCursorPosition(h,c);
}

//main function
int main()
{
    float x=0,y=0,vx,vy,g,fs;

    printf("        Enter the Horizontal Velocity ( Recommended Value : 2.5 ) = ");
    scanf("%f",&vx);
    printf("        Enter the Vertical Velocity ( Recommended Value : 2.5 ) = ");
    scanf("%f",&vy);
    printf("        Enter the Gravity ( Recommended Value : 0.5 ) = ");
    scanf("%f",&g);
    printf("        Enter the Friction ( Recommended Value : 0.025 ) = ");
    scanf("%f",&fs);

    while(1){

            if(GetAsyncKeyState(VK_UP) != 0){ //reset
                system("CLS");
                x=0;
                y=0;
                printf("        Enter the Horizontal Velocity ( Recommended Value : 2.5 ) = ");
                scanf("%f",&vx);
                printf("        Enter the Vertical Velocity ( Recommended Value : 2.5 ) = ");
                scanf("%f",&vy);
                printf("        Enter the Gravity ( Recommended Value : 0.5 ) = ");
                scanf("%f",&g);
        printf("        Enter the Friction ( Recommended Value : 0.025 ) = ");
            scanf("%f",&fs);
            }

            //update
            vy+=g;
            x+=vx;
            y+=vy;

            //check & fix
            if(y+vy>24)
                y=24;

            if((y<15 && y+vy>15 ) || (y>15 && y+vy<15) )
               y=15;
            if(x+vx>78)
                x=78;
            else if(x+vx<0)
                x=0;

                if(y==24 && vx!=0){
                    if(vx>0)
                        vx-=fs;
                    else if(vx<0)
                        vx+=fs;
                }

            if(y>=24 || (x>=10 && x<=35 && y==15))
                    vy*=-1;
            if(x>=78 || x<=0)
                    vx*=-1;

            //draw
            system("CLS");
            if(x>=0 && x<=78 && y<=24 && y>=0){
                gotoXY(x,y);
                printf("O");
            }

            for(int i=10;i<=35;i++){
                gotoXY(i,15);
                printf("*");
            }

            gotoXY(1,1);
            printf("     x = %f , vx = %f  //  y = %f , vy = %f\n\n           Reset : Up Arrow  // Tolga Ay - http://about.me/tolga.ay", x,vx,y,vy);

            Sleep(40);
    }
}